Some nights are full of tossing and turning, leaving you extra tired and in dire need of a jolt of caffeine in the morning. But why? One reason might be your sleep cycle—or, rather, the disruption of it. If you experience disrupted sleep patterns or don’t spend enough time in the deepest, most restorative sleep stages, that’s a recipe for waking up more tired than usual.
Previously, experts believed that once you fell asleep, your body would shut down and become dormant. However, in the 1950s, a professor of physiology at the University of Chicago studied eye movements during sleep and uncovered evidence of sleep cycles. But what are sleep cycles, and how do they affect you? Below, we’ll go over everything you need to know about sleep cycle stages, what sleep cycles are, and how to get a good night’s sleep—every day of the week.
Why Do We Need Sleep?
Before we dive into the various stages of sleep and sleep cycles, it’s essential to know why we need to sleep in the first place. You may consider sleep as a time to wind down and rest, but it’s an extremely active period characterized by rejuvenation, muscle growth, tissue repair, memory retention, and hormone synthesis. Do you ever wonder why you’re so tired when you come down with a cold? It’s because your body needs time to heal and rest with sleep.
The National Sleep Foundation suggests different amounts of sleep for different ages. These suggestions are as follows:
- One-year-olds: 11 to 14 hours
- School-aged children: 9 to 11 hours
- Teenagers: 8 to 10 hours
- Adults: 7-9 hours
Younger children and infants need more sleep since they are still rapidly developing. Language acquisition, motor skill development, social skill growth—these are all areas that are crucial to thriving in life, and sleep helps those skills solidify.
What Are the Stages of Sleep?
When you lie down and begin to doze off into a slumber, your body will go through different stages of sleep. There are four stages comprised of two types of sleep: Non-REM (NREM) and REM (rapid eye movement) sleep. During these stages, various patterns of brain activity take place, triggering restorative processes for the body and mind.
Stage 1 of the sleep cycle occurs as your body prepares to fall asleep. During this stage, your brain produces alpha and theta waves, and your body enters a light stage of NREM sleep. In Stage 1, your body will slow down your:
- Eye movements
- Brain waves
Stage 1 is also the lightest stage of sleep, which means you can easily be woken up by noises, movements, and other environmental factors. The duration of Stage 1 of the sleep cycle typically lasts between one and seven minutes, and you may experience sudden jolts and twitches as your body begins to wind down.
Most of your time spent sleeping is in Stage 2 of the sleep cycle, which is still a light sleep that lasts anywhere between 10 and 25 minutes. During Stage 2, your body’s brain waves, heartbeat, eye movements, body temperature, and breathing continue to slow down to get your body prepared for deep sleep. If you’re an avid catnapper, it’s best to wake up during this stage to avoid feeling tired and sluggish once your alarm goes off.
Stage 2 is also composed of something called sleep spindles and the K-complex. Sleep spindles are sudden bursts of brain activity and get their name from the appearance of their sharp waves on EEG recordings, a type of monitoring method for your brain’s electrical activity. Scientists believe sleep spindles aid in memory formation, cortical development, and help regulate arousal. On the other hand, the K-complex is a sleep-protecting mechanism that promotes sleep maintenance. Both sleep spindles and the K-complex work together to keep your brain and body asleep.
Stage 3 is the beginning of deep NREM sleep, also called slow-wave sleep, and it’s most common during the first half of the night, lessening as the night goes on. On those mornings you feel completely refreshed and ready to go, thank Stage 3. Stage 3 is responsible for restoring your body by replenishing tissues and muscles through the release of growth hormones. This stage is characterized by prolonged, deep, and rhythmic brain waves, which makes it difficult for you to wake up from external factors such as noise. Stage 3 typically lasts between 20 and 40 minutes.
While Stages 1 and 2 consist of eye and muscle movement, they come to a halt in Stage 3. However, movement is possible, which is why sleep disturbances like sleepwalking and night terrors can still occur. And, if you’ve ever woken someone up during this stage, you may have noticed they seemed confused and disoriented for a few minutes before realizing what was going on.
Rapid eye movement (REM) sleep is the final stage of your sleep cycle. It’s called REM because your eyes move—you guessed it—rapidly. The REM stage is characterized by:
- Faster and irregular breathing
- Increased heart rate near waking levels
- Increased blood pressure near waking levels
- Mixed frequency brain wave activity
- Temporary paralysis in arm and leg muscles
- Memory consolidation
As you can tell, a lot of activity occurs during the REM stage of sleep. Have you ever remembered one of those terrifying dreams where you’re falling from your bed? How about one where you’re in a high-speed chase going the wrong way down the highway? When you wake up during the REM cycle of sleep, you’re able to recall your dreams vividly. Luckily, your arm and leg muscles are temporarily paralyzed, which prevents you from acting out your dreams in the real world.
Getting enough REM sleep is vital because it helps in memory consolidation, as well. This is why it’s crucial to create a sleep-inducing environment that limits distractions and encourages relaxation. Whether switching to hypoallergenic bedding to reduce uncomfortable allergic reactions or purchasing a white noise machine to drown out the voices of your city, investing in products to help you sleep soundly will pay off in all areas of life.
What Are Sleep Cycles?
Sleep cycles are the progression between the various stages of NREM sleep and REM sleep throughout the night. Healthy adults who sleep between 6 and 9 hours per night can sneak in about four and five sleep cycles per night.
The first sleep cycle lasts between 70 and 100 minutes, with Stage 3 sleep occupying the most amount of time. The second sleep cycle lasts anywhere between 70 and 120 minutes, but Stage 3 sleep begins to take up less time, while REM sleep begins to increase. As this cycling pattern of NREM-REM sleep continues throughout the night, time spent in REM sleep begins to grow, occurring every 90 to 120 minutes, while Stage 3 sleep begins to decrease.
However, your body doesn’t go from Stage 1 to Stage 2, Stage 3, and REM Sleep and start over from the beginning. Instead, your sleep cycle stages alternate throughout the night between light sleep, deep sleep, and REM sleep. The first cycle of sleep typically starts with Stage 1, where you’re just about to fall asleep, and transitions to Stage 2 of sleep, and then Stage 3.
However, it will sometimes go back to Stage 2 and Stage 3, and then into REM sleep. Throughout the night, Stages 1, 2, and 3 switch back and forth before entering REM sleep. Overall, a recent study found that:
- 5% of total sleep time was in Stage 1
- 50% of total sleep time was in Stage 2
- 20% of total sleep time was in Stage 3
- 25% of total sleep time was in REM stage sleep
How to Sleep Better
Sleeping better isn’t just about getting your recommended 8 hours of sleep. If you want to improve the quality of both your sleep and your life, it’s important you understand the sleep stages and sleep cycles. You could be getting the recommended 8 hours of sleep per night, but if that sleep is only spent in Stages 1 and 2 due to disturbances in your sleep, you could face a variety of adverse health consequences, such as depression and anxiety. Layla Sleep is here to help you get your best sleep, so your days are filled with energy and verve.